The invention relates to a locking cylinder with a cylindrical housing, of which the core bore receives a cylindrical core having a key channel, with core pins located in the cylindrical core, and displaceably guided housing pins in housing pin bores, the housing pins being biased by springs in the direction of the core pins, and with at least one core-adjacent additional tumbler element moveable, in a cavity which intersects the rotational interface of the cylindrical core by a wide-side profile of the key, the tumbler element being spring-loaded in the outward direction of the core, and having a control projection extending sidewards into the key channel.
A locking cylinder of the kind discussed herein is known from GB 112 761, in which the additional tumbler element has a tubular section, on the outside of which, extending along the tubular part, a hook-like portion is applied. The longer hook portion extends parallel with the key channel and there supports a spring in the form of a compression spring, which spring-loads the additional tumbler element in the outward direction of the core so that it reaches an abutment position. The shorter hook portion, running approximately at right angles to the longer hook portion, provides the guiding projection which extends into the key channel. With its tube-like section the tumbler element surrounds a tumbler consisting of a core pin and a housing pin such that, when the key is withdrawn, the tube-like section of the tumbler element intersects the rotational interface of the cylindrical core. The arrangement of the tumblers takes place by way of lock notches cut into the edge of the key whereas the mounting of the tumbler element takes place by way of a longitudinal groove in the wide side of the key. In addition to having a shape which is costly to manufacture, there is the disadvantage that if the additional tumbler element should be displaced in the release direction past the rotational interface of the cylindrical core, no further locking will occur, thus diminishing the security of such a locking cylinder.